This invention relates generally to a system for controlling power to a play feature utilized in coin operated games and, more particularly, relates to a system for adjusting the average amount of current supplied to a solenoid used to move a play feature in a pinball game in response to variations in line voltages for the purpose of attaining uniformity of movement.
Currently, pinball machines utilize unregulated power supplies to minimize costs where the DC output of these power supplies are dependent upon the AC line voltage to which the machine is "plugged into." Unfortunately, it is known that line voltages from municipal supplies may vary by as much as 15% from the specified or nominal voltage which variations randomly occur from time to time and from place to place and, therefore, are unpredictable. Since, the DC voltage generated by the power supply is utilized in particular to supply power to the solenoids used to control game features, any variations in the line voltage likewise directly affects the expected operation of these game features. For example, variations in the power may result in the diminution of or a surge in flipper strength which clearly affects the uniformity of play or the "feel" of the machine. Furthermore, if the line voltage falls to low, the flippers in particular may be affected to the point where they can no longer impart enough speed on the ball to allow the ball to reach game features positioned at the upper end of the inclined playfield.
To further complicate this problem, pinball machines which have large numbers of lamps which are frequently switched on and off have an electrical load which fluctuates. This internal fluctuation in the electrical load also functions to vary the power capable of being supplied to the solenoids. In addition, if the pinball machine is connected to a long branch circuit, or if multiple games are connected in a single branch, a variation in the power requirements of any of the other devices on the line also produces additional fluctuations in the line voltage which affects the machine.
Currently, in an attempt to solve this problem and compensate for any losses in line voltage, pinball manufacturers employ solenoids which are designed to have supplied thereto more current than is required to operate under normal conditions whereby normal operation is possible during conditions of low line voltage. However, this overdesign has been seen to accelerate solenoid wear especially during those instances where line voltage surges above nominal. A further solution was proposed in U.S. Pat. No. 4,209,826 to Priegnitz which sought to regulate power through the use of a high frequency switching power supply which supplied regulated DC voltages to every feature of an entire game. Unfortunately, this system suffers from the main disadvantage of being very costly to implement. As such, an unfulfilled need exists for a pinball machine having the ability to compensate for variations in the line voltage which system can be implemented at a minimal cost.
As a result of this existing need, it is an object of the present invention to provide a power system which can regulate power to selected play features.
It is a further object of the present invention to provide a power system which regulates power synchronously with the AC line cycle.
It is yet another object of the present invention to provide a power system which will allow pinball machines to be shipped with solenoids chosen for the optimum power thereby reducing wear which would otherwise result from overdesign.
It is still a further object of the present invention to provide a power system which will maintain the consistency or "feel" of the game despite line voltage variations.
It is still another object of this invention to provide a power system which will accommodate the use of an unfiltered DC power supply.